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01-28-2002, 01:27 AM #1
Hoping someone can provide some advice. I'm planning to build a bead blast cabinet for occasional use. I've had experiences using low end cabinets driven by 2hp (true 2hp) that don't have enough air, siphon systems that don't siphon, etc. Felt like sandblasting with an air brush.
What's the best way to match things up and get the most blast from the limitd air I have available (about 13-14 cfm)? I was planning to buy one of the cheap Sears portable siphon sandblasters and use that for the gun.
I have two compressors. One is an Emglo contractor type 220 volt rated at 13.5 cfm at 125 psi and 13.8 cfm at 100 psi. Small tanks on this, but 4 cylinders single stage and reputed to have accurate cfm rating. Motor is only 3hp, but it's huge, compressor rated 1.2 or so duty cycle, and Emglo suggests a 30amp 220 volt circuit. I can keep the air fairly dry, though a long run of 3/4 copper pipe, a drain, and a filter. The other compressor might possibly be worth piping in, but it's only a cheap 3-4 cfm portable. Probably not worth the effort, unless there's a magic gun that wants 15 cfm instead of 13?
Any suggestions to match things up?
01-28-2002, 03:56 AM #2
Sorry Pete, but there's really no good answer to this.
I ran my blast cabinet on 6hp with a 60gal tank and it would run out of air rather quickly. I now have a 10hp 120gal setup that just makes it. Blasting is all about air.
The only thing I could suggest is getting one of those guns with the hopper built in (gravity fed) and placing it in your cabinet.
You will still run out of air quickly, but at least you'll get some media through before you have to wait for your machine to cycle up again.
Best of luck
01-28-2002, 12:10 PM #3
I have been fighting low air for years with my blast cabinet. As others said there is no good answer. You can buy lower CFM guns but they won't siphon well. I have a Sears gravity system with the large external hopper. I tried it and it worked poorly. It would clog and /or just not put out media.
J&L had a 7 or 8 CFM gun I am useing which works but throws a fairly smalla mount of media.
I used a cheap gravity blaster with the jug above the gun. It worked real well for me but you go through a quart of media fast unless you are using small parts.
01-28-2002, 04:51 PM #4
Thanks Sean and Kent for the info. The amount of blasting I do (now borrowing a friend's rig) doesn't justify getting a larger compressor -- the two I have do everything else I need. So, I'm wondering if anyone can help with a couple follow up questions.
1) Has anyone used the TP Tools (tptools.com)S-25 or C-25 sandblasting guns? They suggest that this gun fitted with their 10-15 cfm nozzle would work fine if the pressure is set around 80 psi. Or are there other recommended guns?
2) Instead of siphon feed, has anyone tried feeding from a gravity hopper above the blast cabinet or from a pressure hopper (I've seen several under $100) into the cabinet? I'd still run a vacuum to the cabinet and exhaust it outside. I'd rather drain the cabinet and refill a hopper every 20 minutes or so than deal with clogged siphons, poor media pickup, etc. Would either of these alternatives be a step up in effectiveness?
01-28-2002, 10:37 PM #5
I used a gravity setup with the craftsman gun and a large external hopper. It worked OK but is still a small amount of media expelled compared to the commercial setups I have used. It is better than nothing and if you only do ocassional work the extra time to blast shouldn't be a problem.
01-29-2002, 12:38 AM #6
I have had several "sandblasters" in my lifetime and non ever worked very good including my Sears which I dumped 15 years ago in a yard sale for $20. I did not get satisfaction until I bought a "real" 24X36 in ch blasting cabinet that uses glass beads, not sand. Since the glass beads are smaller and lighter than the sand I think the guns also use less air. When using my gun full time my compressor is just loafing and runs only about 1/2 the time to keep the tank up. My compressor is a 3 phase 5 hp with a 60 gal tank. I blast most stuff at 125 psi and all the glass beads just get recycled so do not have to keep adding. I use the cabinet about twice a week or so and have been doing that for 17 years. The original ceramic nozzle does not appear to be anywhere near wearing out. I offer this for info only as I know you probably do not have need for this elaborate setup and if purchased new now I think I would have to spot $1000 for the cabinet and $700 or so for the compressor. I also have a Sears Vac picking up the dust so do not get 100% recycled beads.. some beads turn to dust and get picked up by the vac. I am guessing about 95% of the beads do get recycled tho. I go through a 50 lb bag of beads about every 5 years and a bag is about $35. $7. a year to run. I have never used an air dryer. The water in the system never plugs anything up, but do notice when I use it the first few seconds my gloves are wet.
01-29-2002, 01:04 AM #7
I've never personnaly had a good setup but, I've heard a pressurized hopper makes a big difference. All of the big industrial units are set up that way. The booth we have at work, using steel shot will dissolve 1/4" plate.I would recommend checking into the pressurized system if you have the chance. That way you don't waste your valuable CFM sucking up sand and all the air gets used to blast instead.
01-29-2002, 01:21 AM #8D. Thomas Guest
My EconoBlast used to clog often, so I would disconnect the bead tube and connect it to the gun output and shot air backwards thru the tube. This would clear the flow for awhile. I'm using a Trico cabinet now, and for some reason it's gun almost never clogs. Could be just less humidity in a different shop...dunno. Used 5 hp compressors with each. In the Ripley's Believe it or not dept. a bird entered my shop thru a gap between the roof and wall, and built a nest in one of the gloves !
01-29-2002, 02:18 PM #9
A faster way when they clog is to just put the glove over the nose of the gun and pull the trigger or pedal or whatever.
I have had good luck with non pressurized unit. I don't remember the compressor size but it was HUGE. I mean 6' long and over 3' in diamiter. When the motor is running you could feel the ground shake 15' away.
I have had the oposite results than the metal doctor. The fine glass bead would jam on me and the 80 grit oxide did not. Go figure.
01-30-2002, 12:30 AM #10
Thanks, everyone, for your ideas and experience. I'm planning to borrow a cheap pressure unit and try it. Will also probably buy the TP tools gun.
02-21-2002, 01:18 AM #11
Pete, I have the TPtools 'Skatblast' 400, or some such, cabinet with that gun. It works just dandy with my 11cfm compressor (IR 5HP, single stage, 60gal.) I think the more important aspect of the compressor may be wether it's continuous duty rated or not. Use the small or medium nozzles.
02-21-2002, 10:27 PM #12
I have a old Sears compressor 3hp, have used the siphon type of sandblaster, used TONS of air. I recently got a cheap pressurized 90lb unit, makes a world of difference, less air, more of a pattern, faster cleaning action. Even a cheap pressure type is vastly better than a siphon type.